Apple could unveil two new iPhones this year -- one with a 4.7- or 4.8-inch screen, the other with a 5.5-inch display, according to recent rumors. Assuming those rumors are true, the larger edition is reportedly facing production delays over its battery, claims Taiwanese news site Commercial Times.

Apple wants to outfit the larger phone with a thin body, according to the Commercial Times, as reported by GforGames. But that goal apparently poses challenges for battery makers. Smartphone batteries typically are 2.8mm to 2.9mm thick. But the battery for the big-screened iPhone would need to be 2mm or less.

As such, the 5.5-inch iPhone 6 may not see the light of day until 2015, or at least until battery makers can meet Apple's strict requirements. The smaller-screened iPhone would presumably still roll out in September per Apple's usual launch time frame.

Since the term "5.5-inch iPhone 6" doesn't exactly roll off the tongue, Apple suppliers have supposedly already dubbed it the iPhone Air, says Commercial Times. But the report refers to that label as a "nickname," so it's not one that Apple will necessarily adopt.

For now, file all of this in the rumor department. But given the huge demand for large-screen phones, it's a safe bet Apple will bump up the screen size on at least one new iPhone this year.